Process for coking hydrocarbonaceous liquids



Nov. 19, 1957- E. GORIN PROCESS FOR COKING HYDROCARBONACEOUS LIQUIDSFiled March 9, 1955 GAISES HYDROOARBONACEOUS RE YOLE GASES I LIQUID g 220 I I 26 1 PRIMARY SECONDARY I6 I VAPOR LTREATING TREATING AQ Q L ZONEZONE I SWEEP 2 GAS 950- 950- I200F I600F LIQUID women I? l2 FIG. I QHIGH ASH Low ASH I cox: COKE PITcI- GASES HYDROGARBONAOEOUS REOYGLEGASES LIQUID 4| .40

I Q Q 3 PRIMARY VAPOR i aa- 1'45 RECOVERY 3| TREATING zone SECONDARY 42sweep 950- TRZEATIENG GAS F 32 LIQUID .950- PRODUCTS I600F a? 44 39 VFIG. 2 PITCH HIGH ASH Low ASH COKE cox:

" INVENTOR. EVERETT GORIN BY ATTORNEY United States Patent'Q i PROCESSFOR COKING HYDROCARBONACEOUS LIQUIDS Everett Gorin, Pittsburgh, Pa.,Consolidation Coal Company, poration of Pennsylvania assignor toPittsburgh Pittsburgh, Pa., a cor- The present invention relates to aprocess for coking ash-containing hydrocarbonaceous liquids- Moreparticularly, it relates to a process of the continuous type forpreparing low-ash-content coke -from high-ash-content hydrocarbonaceousliquids.

Hydrocarbonaceous liquids, especially those derived through pyrolysis ofcarbonaceous solids, frequently contain substantial quantities of finelydivided solids which are ditficult to remove. These finely dividedsolids are particles of the original carbonaceous solids and partiallypyrolyzed solids which become entrained in the pyrolysis vapors. It isnot unusual for low temperature coal carbonization liquid products, forexample, to contain as much as 15 to 25 percent by weight of thesefinely divided solid particles which contain all of the ash originallypresent in the particles prior to carbonization. 'The ash composition ofthese particles may be as much as to percent by weight.

As used herein, ash is defined as the non-combustible inorganic residuewhich remains following exhaustivecombustion of the material. I

Cokes produced by thermal treatment of these ash-containinghydrocarbonaceous liquids cannot be marketed as premium carbon sourcesbecause of their high ash contamination. The same problem arises inconnection with utilization of the products of liquid phase coalhydrogenation, the liquid product resulting from solvent extraction ofcoal, the liquid product from'oil shale pyrolysis, and like materialshaving relatively high-ash content.

To utilize these hydrocarbonaceous liquids as a premium solid carbonsource, for use as an electrode carbon, for example, they must beconverted into a coke having essentially no ash. Filtration ofash-containing solids from the hydrocarbonaceous liquids is diificultand expensive, if possible at all. The fine state of subdivision of thesolids results in plugging of the pores of conventional filters; theviscous character of the liquids requires preliminary heating to permitpassage through filters. Hence filtration is ordinarily not practiced.

Frequently the more valuable lower boiling liquid con- ;stituents ofthese hydrocarbonaceous liquids are first re- .covered as product bydistillation. The undistilled resi- .due of such distillationhereinafter will be referred to as pitch. In some instances, forexample, this undistilled residue boils above 230 C.; in other instancesthe undistilled residue boils above 300 C.; the precise temperature ofseparation is determined by the proportions of the starting material andthe demand for the lower boiling material. The high boiling undistilledresidue usually is referred to as pitch.

I have discovered a method for preparing low-ash carbon solids fromhigh-ash hydrocarbonaceous liquidsby a -two stage thermal treatment. Thehigh-ash liquid is rather than the batch type.

v treatment zone separating non-condensable subjected to a primarythermal treatment under mild cok I 2,813,824 latented Nov. 19, 1957in'gconditions at 950 to 1200 F. for preparinga high-ash coke containingessentially all of the ash-containing solids in -the' starting liquidtogether with a small portion of coke derived through thermaldegradation of the more readily cokable constituents of the liquid. Theuncoked components of the original liquid are recovered from the primarythermal treatment in vapor form, essentially free of ash containingmaterials. All or a portion of these uncoked vapors are subjected to asecondary thermal treatment under more severe coking conditions at 950to 1600 F. The secondary thermal treatment produces an ash-free cokesuitable as a premium carbon source together with non-condensable gases,low boiling liquid products, and an ash-free liquid residue which may berecycled to the secondary thermal treatment for further coking or may berecovered as a premium quality pitch, if desired. The ash-containingcoke produced in the primarythermal treatment may be used as a fuel oras a low grade source of carbon,'such as used in carbide production,metallurgical installations, and the like.

By the term coal as used herein, I comprehend all ranksof coal includinganthracite, bituminous, sub-bituminous, lignite and the like. Thepresent invention also finds utility in the treatment of liquid productsresulting from the pyrolysis of oil shale.

The present process is applicable to those coking systems which aresusceptible to controlled fractional coking, i. e., those systems whichare of the continuous type The extent of coking which results in batchprocessing cannot be controlled withthe precision required to realizethe benefits of the present invention. Examples of batch processes arethe sole-heated ovensin which a cokable, high boiling, hydrocarbonaceousliquid is heated under quiescent conditions to produce a solid block'ofresiduum coke. Examples of continuous type processes are those cokingsystems carried out in fluidized beds, in moving solids' beds, inrotating kilns and the like. i

For a clear understanding of the present invention, its objects andadvantages,'reference should be had to the following description andaccompanying drawings in which:

v Figure 1 is a flow sheet illustrating the preferred embodiment of thepresent invention; and

Figure 2 is a How sheet illustrating an alternative method for carryingout the present invention.

The apparatus shown schematically in Figure lincludes a source ofhigh-ash-feedstock 10; heaters 11 and 12 for raising the temperature ofliquid feedstock; a primary thermal treatment zone 13; a secondarythermal 14; and a vapor recovery system 15 for gases, liquids andunconverted pitch.

The material used as a feedstock in the present process is ahydrocarbonaceous liquid containing ash. The process is especiallyapplicable to treatment of that fraction of low temperaturecarbonization tar boiling above 300 C. as well as treatment of theentire liquid product from low temperature carbonization, although it ispreferable to remove at least the valuable constituents boiling below230 C. for recovery prior to thepresent treatment since these materialsare susceptible tothermal degradation to less valuable materials. Thefeedstock, quite viscous at ordinary temperatures, may be heated tofacilitate its pumping through pipes. A heater 11 is provided for thispurpose. The amount of preheat should be .sufficient to reduce theviscosity of the liquid to permit heater. lreferablythe liquid ispreheated to a temperature in the range 200 to 800 F.

Preheated hydrocarbonaceous liquid is introduced into the primarythermal treating zone 13, maintained at a temperature of 950 to 1200 F.This primary treating zone is a suitable coking unit of the continuoustype, c. g. 'a fluidizedpitch coker, a downward1y movirig bed pitch"coker, a rotating kilnjapugmilhzarid'the like. Thepri- 'mary zone13contains amass of heated carbonaceous pebbles. These carbonpebblessupply the necessarysur- "face area for depositionfof a layer ofcoke from the liquid ffe'edstock. It may be necessary'fromtimeto'tirneto supply additional seed pellets as nuclei for theformation of additional carbon pebbles. Sweep-"gas is'introducedinto'the'primary treating zone 13 through'a'conduitflsto allow regulation ofthe extentof' coking occurring" therein. The 'sweep'gas serves to reducethe partial pressure of the vaporized feedstock and to facilitateremoval ofthe vapors from the primary treating zone 13. 'Recycleproductga'ses are preferred assweep' gases. The'temperature; residencetime and sweep gas rate in the primary-zonal? arereg'w lated toallowonly a minimum coking of the liquid portion of the feedstock.

As feedstock is introduced into the-primary treating bed "of carbonpellets, a film of liquid feedstock forms on the surface of eachpebble.The substantial bulk of the feedstock is volatilized and recovered as avapor through conduit 16. The finely divided ash-containing'parti'clesof the feedstock adhere to the moist surfaces of the carbon pellets andare incorporated into the carb onpellets-during the subsequent coking ofthe liquid film resulting from its continued exposure to co ngconditions in'the primary zone 13. A portion of the carbon pebbles fromthe' first zone is removed continuously or intermittently from the 'bedfor screening. Oversize pebbles are removed as'product high-ash coke andundersize pebblesare returned to the primary zone for additional sizeaccretion'through further coking. I prefer'tolimit production'of-high-ash coke in the'primary zone to about 5 to percent ofthe liquidportion of the feedstock by weight.

The total vapors resulting'from :the primary thermal treatment zone arepassed'throughpaconduit 16 to a-secondary. thermal treating zone 14,operated under-more severe coking conditions at 950 to 1600 F. In thepreferred embodiment shownin Figure 1; thersecondarygtreating zone 14may function as a; liquid eoker or may function eoncurrently as a'liquid coker and as a retormerto upgrade in quality the uncoked productsfrom the primary treatment. Where the secondary, treating zone is to beoperated as a concurrent liquid coker and reforrrien its temperatureshould be maintained in the range of 1300 to 1600" Where the secondarytreating zone is operated as a liquid coker, its temperature should bemain- .tained in the: range of 950 to 1200? F. to avoid thermalconversion of the 1uncoked constituents. The;temperature of thesecondary treatment zone (as aliquidcoker) need not necessarily behigherthan that of theprirnarytreat- ,ment zone since the extent of cokingcanjbe effectively regulated through control of the sweep gas rate andvap'or residence time. The secondary treating zone 14'c'oiit'ains aheated mass of carbon pebbles'which su ply the necessary surface for theadditional "coke: formation. The pebbles in this instance are premium;essentially ash-free, carbon pellets. p I i The vapors entering thesecondary treating zone 14'are essentially ash free. A" portion'of thevapbrscon'clenses to form a film upon the surface of the earbonpelletswhich 7 is converted into coke on extended exposure to the processingconditions in the secondary 'zone'14; When thesecondary treatment zone14 is operatedfas a concurrent liquid coker and reformer, the uncokedcomponents of the liquid experience a beneficial reforming which resultsfrom the severe .thermal conditions maintained in the secondary zone 14.The resulting uncoked vaporsiarerecovered "through a conduit'ls. Aportionof the solid -pellets in 5 rently satisfied by high 'Ifdesired, aportion of the'ash-free reformed pi'tchmay be recycled through a conduit24and heater 12 for further 4 coke" production and reforming in thesecondary thermal i preventing its recycle may beconductedunderfluidized conditions. 'i'zed technique provides a sweep gas rates tocontrol maryzone. To produce the'lump form coke product de- 1 'manded inthe market, the secondary thermal treating zone -may be operated as a 4the secondary zone 14 is removed continuously or intermittently througha conduit 19 and screened. Oversize pellets are recovered as product,low-ash, premium carbon; undersize pellets are returned to the secondaryzone 14 for additional size accretion through further coking.

The ash-free vapor product from the secondary treatment zone 14 passesthrough a conduit 18 to the vapor recovery system 15. Non-condensablegases are recovered through a conduit 20 for further processing, for useas fuel or for disposal. If desired, a portion of the noncondensablegases may be returned through conduits 21 and 26 to provide the sweepgas for controlling the coking rate'in'the primary treatingZone 13 andthe secondary treatingzone 14 respectively. Low boiling liquid productsare recovered through a conduit 22, e. g. those boiling below 300 C.High boiling residue, e. g. pitch boiling above 300 C., is recoveredthrough a conduit 23 as an ash-free reformed pitch. This reformed,ash-free pitch is valuable in itself as an electrode binder, animpregnant, a roofing material, or any of the similarapplicationscurtemperature carbonization pitches.

treating zone 14. A portion of the pitch in conduit 23 -'--niust-be'-'removed as' product since the thermal treatment introduces a refractoryproperty to the ash-free pitch, to extinction via continued coking.

Toavoid the operability problems which'arise from the used a moving bedcontacting technique for the primary coking' process,"the primarythermal treatment zone 13 The fluidconvenient means for regulating theextent of coking in the pridownwardly moving bed. The alternativeembodiment of the present invention 3 illustrated in Figure 2 is adaptedto the treatment of ash- #liquids' without the'necessity l valuablelowboiling constituents.

containing .hydrocarbonaceous liquids and particularly to the treatmentof a wide boiling range fraction of said for preliminary removal of Theapparatus shown in Figure 2 includes a-source of feedstock 30; heaters31 and 32 for elevating the temperature of liquid feedstock;

- a' 'primary-thermal treating zone 33; a .secondarythermal treatingzone 34; and a vapor primary thermal treatment zone recovery system 35.The 33, in structure, operation and function corresponds to the primaryzone 13 of Figure l.

- Feedstock fromthe source 30 is heated in the heater 31 to a'pumpabletemperature andsubjected to mild coking conditions at 950 to l200 F. inthe primary thermal treatment zone 33. High-ash coke pellets arerecovered through a conduit 37. Uncoked vapors are recovered through aconduit 36 and sent directly .to the vapor recovery system 35 forrecovery of non-condensable gases through a conduit 40 and recovery oflow boiling liquid products through aconduit 42. By avoiding treat-'ment of these vapors under the more severe conversion conditions ofthesecondary treating zone 34, loss of valuable low boiling tar acidsfrom the feedstock is minimized. High boilingresidue pitch, ash-free, isrecovered 41' 3116 45 to each of the through a conduit 43 and passed tothe secondary thermal treating zone 34- through a conduit 44 and heater32. The secondary treatment zone 34, operated at a temperature of 950to1600 F.,' corresponds in structure, operasecondary treatment zone 14shown in Figure l.- Low-ash coke pellets are recovered through a conduit39 and volatilized portions of the ash- '-free pitch are recoveredthrough a conduit 38 and fractionated in the vapor recovery system 35.-'Recyeling-- of non-condensablegases through. conduits thermaltreatment zones, permits independentcontrol over the coking rateoccurring in each of the treatment zones.

To illustrate the present invention, according to Figure 1 will bereported The feedstock was low temperature carbonization pitch boilingabove 230 C. The pitch, produced in a fluidized low temperaturecarbonization process, contained 9 percent solids by weight and 0.78percent ash by Weight. Pitch, preheated to 320 F., was passed downwardlythrough a primary coker maintained at 1000 F. and containing adownwardly moving bed of devolatilized coke pellets which had beenscreened to pass through a standard No. 8 mesh and be retained on astandard No. 16 mesh. The pellets were prevented from adhering throughthe action of a rotating stirrer.

For every 100 lbs. of pitch feedstock, 16.8 lbs. of highash coke wereproduced in the primary coker vessel. This product coke had anash-content of 4.5 percent by weight. 97 percent of the ash in thefeedstock appeared in the product coke.

83.2 lbs. of vapors were removed from the primary coking vessel andpassed without condensation upwardly through a secondary reformingvessel containing a downwardly moving bed of devolatilized coke pelletswhich had been screened to pass through a standard No. 8 mesh and beretained on a standard No. 16 mesh. The reformer was maintained at atemperature of 1450 F.; no mechanical agitation of the bed was provided.The 83.2 lbs. of primary coker vapors were subjected to the reformerconditions for a contact time of 4 to 5 seconds. 20 lbs. of low-ash cokeand 63.2 lbs. of vapors were produced in the reformer vessel. Productcoke pellets from the secondary zone had an ash content of 0.115 percentby weight. 20 lbs. of ash-free pitch boiling above 230 C. were availablefor recycle or for use as premium quality pitch. 43.2 lbs. of gas,liquor and low boiling distillates were recovered.

A material balance for the described operation is presented in Table I.

results of operation by way of example.

43.2 lbs. gas, liquor and distillate.

The original feedstock contained 9 percent by weight of solids in whichthe ash constituents were concentrated. Based on the 91 lbs. of liquidpitch in the feedstock, 18.6 percent by weight was converted to ahigh-ash coke and 22 percent by weight was converted to a low-ash coke.An additional 22 percent by weight of the liquid portion of thefeedstock was recovered as a pitch available for the production ofadditional coke by recycling if desired.

According to the provisions of the patent statutes, I have explained theprinciple, preferred construction and mode of operation of my inventionand have illustrated and described what I now consider to represent itsbest embodiment. However, I desire to have it understood that, withinthe scope of the appended claims, the invention may be practicedotherwise than as specifically illustrated and described.

I claim:

1. The method of preparing low-ash coke from an ash-containinghydrocarbonaceous liquid which comprises passing said liquid through afirst mild coking zone at 950 to 1200 F., recovering a high-ash coketherefrom, separately continuously removing therefrom the uncokedportion of the feedstock as a substantially ash-free vapor, passing atleast the high-boiling portion thereof through a second thermal treatingzone at 950 to 1600' F., re-

6 covering a; low-ash coke and 1 separately continuously .removing theuncoke'd vapor from said second "zone.-

2. The method of preparing low-ash coke from an ash-containinghydrocarbonaceous liquid boiling above 300 C. which comprises passingsaid liquid through a first mild coking zone at 950 to 1200 F.,recovering a high-ash coke therefrom, separately continuously removingtherefrom the uncoked portion'of the feedstock as a substantiallyash-free vapor, passing, of said ash-free vapor through a second thermaltreating zone at 1300 to 1600 F., recovering a low-ash coke andseparately continuously recovering uncoked vapors from said second zone.

3. The method of preparing low-a sh coke from an ash-containinghydrocarbonaceous liquid boiling above 300 C. which comprises passingsaid liquid through a first mild coking zone at 950 to 1200.F.,recovering a high-lash coke therefrom, separately continuously removingtherefrom the uncoked portion of the feedstock as a substantiallyash-free vapor, passing all of said ashfree vapor through a secondthermal treating zone at 1300 to 1600 F., recovering a low-ash coketherefrom, separately continuously removing therefrom the uncoked vaporsfrom said second zone, recovering non-condensable gases from saiduncoked vapors and recycling at least a portion thereof to said firstmild coking zone as sweep gas for limiting high-ash coke productiontherein to 5 to 15 weight percent of the liquid portion of thefeedstock.

4. The method of preparing low-ash coke from an ashcontaininghydrocarbonaceous liquid which comprises passing said liquid through afirst mild coking zone at 950' to 1200 F., recovering a high-ash coketherefrom, separately continuously recovering therefrom the uncokedportion of the feedstock as a substantially ashfree vapor, recoveringnon-condensable gases, low boiling'distillate and high-boiling residuefrom said ash-free vapor, passing said high-boiling residue continuouslythrough a second thermal treating zone at 950 to 1600 F., and recoveringa low-ash coke and separately continuously recovering the uncoked vaporsfrom said second zone.

5. The method of preparing low-ash coke from an ash-containinghydrocarbonaceous liquid which comprises passing said liquid through afirst mild coking zone at950 to 1200 F., recovering a high-ash coketherefrom, separately continuously recovering the uncoked portion of'the feedstock as a substantially ash-free vapor, recoveringnon-condensable gases, low-boiling distillate and high-boiling residuefrom said ash-free vapor, passing said high-boiling residue continuouslythrough a second thermal treating zone at 950 to 1600 F., recovering alowash coke and separately continuously recovering the uncoked vaporsfrom said zone, recycling at least a portion of said non-condensablegases to said first zone as sweep gas for limiting high-ash cokeproduction therein to 5 to 15 weight percent of the liquid portion ofthe feedstock.

6. The method of preparing low-ash coke pellets from an as -containinghydrocarbonaceous liquid which comprises passing said liquid at 950 to1200 F. through a first mild coking zone containing a bed of particulatecarbonaceous solid pellets, passing sweep gas through said first zone tocontrol deposition on the pellets therein of a coke layer containing 5to 15 percent by weight of the liquid portion of the feedstock togetherwith substantially all of the ash from the feedstock, recovering a.high-ash coke from said first zone, separately continu-- ouslyrecovering therefrom the uncoked portion of the,: feedstock as asubstantially ash-free vapor, passing said ash-free vapor at 1300 to1600 F. through a second. thermal treatment zone containing a bed ofparticulate, essentially ash-free carbonaceous solid pellets,recovering. essentially ash-free carbonaceous solid pellets from saidsecond zone, retaining uncoked vapors in said second.

said second zone. 7. The methodof claim 6v in which the asheontaiminghydrocarbonaeeous liquid is derived from-coal. 5

References Cited in the file of this patent UNITED STATES PATENTS1,963,265 Fisher et a1 June 19, 1934 10 '8 'A'lbe ding Aug. 14, 1-934Ramsburg Aug. 28, 1934 Atwell Dec. 15, 1936 Lefier v- Aug. 31, 1954Findlay Nov. 9, 1954 Adams Dec. 28, 1954

1. THE METHOD OF PREPARING LOW-ASH COKE FROM AN ASH-CONTAININGHYDROCARBONACEOUS LIQUID WHICH COMPRISES PASSING SAID LIQUID THROUGH AFIRST MILD COKING ZONE AT 950 TO 1200*F., RECOVERING A HIGH-ASH COKETHEREFROM, SEPARATELY CONTINOUSLY REMOVING THEREFROM THE UNCOKED PORTIONOF THE FEEDSTOCK AS A SUBSTANTIALLY ASH-FREE VAPOR, PASSING AT LEAST THEHIGH-BOILING PORTION THEREOF THROUGHH A SECOND THERMAL TREATING ZONE AT950 TO 1600*F., RECOVERING A LOW-ASH COKE AND SEPARATELY CONTINUOUSLYREMOVING THE UNCOKED VAPOR FROM SAID SECOND ZONE.